This invention refers to a digital feeding speed controlling encoder for a circular knitting machine. Generally, the feeding part of an encoder is divided into passive and positive or active forms, of which this invention is mainly concerned with the positive or active form. The positive or active mechanism feeds automatically a certain length of yarn into the knitting section. It is commonly adopted by a conventional device on the main structure called a quality pulley, due to its being able to adjust the yarn tension.
A conventional encoder adjusts the notches of the quality pulley disc to control the density of the textile from different materials. In addition to mobilizing the knitting pins, the main motor of an encoder, by way of a gear-transmission to activate the belt around the pulley disc, surveys several feeding devices and hence progressively feeds the yarn into the knitting pins to increase productivity. Since accelerating the belt speeds up the feeding, the pulley disc operation control turns out primary. Nevertheless, lacking such numerical control, conventional encoders must rely on manual operation to control the textile density by employing skilled workers to stop or adjust the machines whenever necessary. In this case, in the production process, the machines have to be stopped in order to adjust the pulley disc, i.e., using a tool to loosen the bolt of the pulley disc, rotating the disc clockwise or counterclockwise to change the diameter of the segments in the disc, then re-starting and working the connected belt to make the encoder feed the yarn.
As shown in FIG. 1, the quality pulley disc (1) described above is comprised of twelve trapezoidal cubic segments (11) that are assembled in a circular arrangement. The segments are pressed together tightly by two round discs (12), (13). Between the upper disc (12) and the segments, there are twelve slots running outwards from the center. On the other side, the disc is closely connected with the spiral slots of the lower disc (13). When turning the upper disc (12) and leaving the lower disc (13) still, the segments, carried by the upper disc (12), will expand or contract according to a change in the perimeter of the circular quality pulley disc and also change the speed of the belt accordingly. Since the length of the belt is constant and the belt itself is non-extensible, a belt-tension-controlling device is needed to avoid the sliding difference phenomenon, which causes the problem of mal-distributed or uneven textile density. Therefore, the conventional encoders take a lot of time to stop and check repeatedly whenever the knitting density is not stable. For example, the conventional encoder, as shown in European patent EP00894884 has to separately adjust the tension of the belt to sustain even feeding. To improve the shortcoming of conventional encoders, this invention provides a better feeding method and apparatus.
This invention, primarily, provides a precise digitally controlled feeding device to replace the conventional speed control and belt-tension control to thereby obviate the need for manually altering the pulley disc and belt tension and certainly decreases the production standby time.
Now the features and advantages of the invention will be described in detail with reference to the accompanying drawings.